1. Field of the Invention
The present invention generally relates to signal transmission in a communication system, and in particular, to a data transmission method and apparatus capable of compensating for distortion caused by fast fading in a communication system that uses a Space-Frequency Block-Coded (SFBC) scheme and a single carrier.
2. Description of the Related Art
In the next generation multimedia communication system now under research, as there is an increasing demand for a high-speed communication system capable of processing and transmitting a variety of information such as video and wireless data beyond early voice-oriented services, it is necessary to increase efficiency of communication systems by using a proper channel coding scheme. In addition, communication systems should transmit signals over a channel at high efficiency and reliability.
Meanwhile, wireless channel environments in wireless communication systems, unlike wire channel environments, suffer a loss of information as errors occur due to various causes such as multi-path interference, shadowing, propagation attenuation, time-varying noise, interference, fading, etc. A Frequency-Domain Equalization (FDE) scheme has been proposed as a technique for removing interference in the wireless channel environments.
In addition, a single-carrier transmission scheme based on the FDE scheme has recently been adopted as a standard for the broadband wireless Metropolitan Area Network (MAN) system, such as Institute of Electrical and Electronics Engineers (IEEE) 802.16 and European Telecommunications Standards Institute (ETSI) Hiper MAN. Further, a Single Carrier Frequency-Domain Equalization (SC-FDE) scheme having the similar structure and performance to that of the Orthogonal Frequency Division Multiplexing (OFDM) scheme, is robust against non-linear distortion or synchronization of carriers, and can reduce system complexity of a user terminal for uplink transmission even through simple signal processing at a transmitter.
Also, there has been proposed a transmission diversity technique that can increase channel capacity and link reliability by spatially arranging several transmission antennas without increasing a frequency bandwidth or transmission power. Recently, an SC-FDE scheme to which a Space Time Block Code (STBC) scheme for providing a transmission diversity gain is applied has been proposed.
FIG. 1 shows an STBC transmission sequence used for transmitting signals via two antennas using an STBC scheme according to the prior art. Referring to FIG. 1, the STBC transmission sequence sequentially transmits symbol blocks 110, 120, 130 and 140 via two antennas 101 and 103 in the time domain, and inserts cyclic prefixes (CPs) 112, 122, 132 and 142 between the symbol blocks 110, 120, 130 and 140 as guard intervals. The channel state should be constant between two symbol blocks, i.e. an nth block 110 (or 130) and an (n+1)th block 120 (or 140), transmitted through each of the two antennas 101 and 103. However, the SC-FDE scheme to which the STBC scheme is applied, can guarantee its performance because the constant channel state between symbol blocks is maintained in the slow fading environment, but the scheme has a limitation in performance guarantee in the fast fading environment.
However, the SFBC scheme, although it is robust against the fading environment as compared with the STBC scheme, cannot be directly applied to the single-carrier system because it is a multi-carrier scheme that applies block codes to adjacent sub-channels or adjacent sub-carriers. In particular, the channel state between adjacent sub-carriers should be constant, in order for the SFBC scheme to guarantee its performance.